Switching between white light imaging and excitation light imaging leaving last video frame displayed

ABSTRACT

Still image display of a recent video image of tissue as a reference still image prior to a switch in the mode of illumination of the tissue. The still image is displayed concurrently with live video of the tissue under a different mode of illumination, to facilitate discrimination between healthy and diseased tissue, and further facilitate therapeutic intervention. The reference still image may be displayed either as an insert (picture-in-picture), side-by-side, or the like concurrently with the live video image. In some embodiments, when a practitioner switches a light source from “excitation-light” to “white light”, the “excitation-light” video may be frozen/captured and displayed as a reference still image as a PIP, and the “white-light” live video is displayed concurrently. When the source is switched again, the “white-light” video may be frozen/captured and displayed as a reference still image, and the “excitation-light” live video is displayed concurrently.

FIELD OF THE INVENTION

The invention relates to diagnostic imaging techniques generally, andmore specifically to automatically displaying the last live video imageof tissue prior to a switch in the mode of illumination as a referencestill image. The reference still image is displayed concurrently with alive video image of the tissue under a different mode of illumination tofacilitate discrimination between healthy and diseased tissue and tofurther facilitate therapeutic intervention.

BACKGROUND OF THE INVENTION

Recently, diagnostic endoscopic techniques have been developed toirradiate tissue to be studied with visible light and to detectresulting fluorescent images which are then analyzed for diagnosticpurposes. These techniques have been found particularly useful fordiagnosing disease conditions such as cancers or tissue degeneration andfor highlighting the boundary regions of such conditions under study.These techniques are sometimes enhanced by also studying normal lightimages resulting from reflection of the irradiating visible light(usually white light).

In the case of autofluorescence, i.e., the stimulated emission resultingfrom impingement of the excitation light onto a biological tissue, thefluorescence typically has a longer wavelength than that of theexcitation light. Fluorescent substances within organisms areexemplified by collagens, NADH (nicotinamide adenine dinucleotide), FMN(flavin mononucleotide), pyridine nucleotide and the like. Recently, therelationship between such fluorescent substances and various diseaseshas been recognized, making it possible to diagnose cancers and the likeby use of these fluorescences.

In addition, certain fluorescent substances such as HpD(hematoporphyrin), Photofrin, ALA (delta-amino levulinic acid), and GFP(Green fluorescent protein), are selectively absorbed by cancers andthus may be used as contrast materials. In addition, certain fluorescentsubstances may be added to a monoclonal antibody whereby the fluorescentmay be attached to affected areas by an antigen antibody reaction.

Lasers, mercury lamps, metal halide lamps, xenon lamps, and the like maybe used as and for the excitation light, which may be of a certainfrequency or frequencies or may cover a certain spectrum that is usefulfor Autofluorescence (“AF”), Photodynamic Diagnosis (“PDD”), Indocyaninegreen (“ICG”), or other such known diagnostic techniques. For example,when a light with the wavelength of 437 nm is emitted onto agastrointestinal tract tissue, green autofluorescence by abnormaltissues is attenuated compared to the autofluorescence of normaltissues, but red autofluorescence of abnormal tissues is not attenuatedas much compared to the autofluorescence of normal tissues.

Since the fluorescent images obtained in this way typically have verylow reflective intensities as compared to the reflected images obtainedwith conventional white light, photomultiplication, such as by using ahigher camera system gain factor or increased imager integration time,may be necessary.

Generally, when a blue or ultraviolet light is emitted onto biologicaltissue, an autofluorescence occurs within a longer wavelength band thanthat of the excitation light. Moreover, fluorescent spectra aredifferent between normal tissues and abnormal tissues, such asprecancerous tissues, cancerous tissues, inflammatory tissues anddysplastic tissues, such that the existence of lesions and conditions oflesions can be detected based on subtle changes in coloration of thefluorescent images.

In particular, since with a blue excitation light, the intensitydistribution of fluorescence stimulated near the green region(especially that of 490 nm-560 nm) is stronger in normal tissue than indiseased tissue, emissions in the green region and in the red region(e.g., wavelengths in the 620 nm-800 nm region) are arithmeticallyprocessed to generate two-dimensional fluorescent images, and by thesefluorescent images the discrimination between abnormal and/or diseasedareas and normal areas can be achieved.

In known systems, video images are produced for diagnostic observationof autofluorescent emissions, and adjustments are made to the ratiobetween the video signals corresponding to the green and red fluorescentintensities to allow normal tissues to have a certain color tone.Accordingly, tissue known to be normal is first observed, and the ratiosof the red and green emissions are adjusted to establish a referencecolor tone. Then, after the adjustment of the color tone of the normalparts, the potentially diseased tissue is observed. In this way, thenormal parts are designated with a certain color tone and abnormal partsare designated with different color tones from that of the normal partsdue to the attenuation of the green signal. By the differences in colortones between abnormal and normal parts, the abnormal parts can bevisualized. Typically, the ratio is adjusted so that the normal tissueappears in a cyanic color tone and diseased tissue appears as a redcolor tone.

Moreover, in some fluorescent observation devices, a single light sourceis used both as an excitation light to conduct fluorescent observationsand as a white light to conduct white light observations by insertionand removal of a color filter, either by mechanical or electronic means.As will be understood, when only fluorescent images are desired, thereshould be no illumination by, or detection of, white light, but onlyillumination by and detection of the excitation light. Thus, switchingis required so that when a white light image is to be obtained, a whitelight is emitted and/or detected, and when a fluorescent image is to beobtained, an excitation light is emitted and/or detected.

Further, image switching is typically controlled so that when whitelight is emitted the resulting image is provided only to a white imageimaging device, and so that when the excitation light is emitted, thefluorescent image is provided only to a high-sensitivity fluorescentimaging device.

Generally, since the subtle variations in coloration of fluorescentimages are subjectively visualized by a medical practitioner, the lackof fixed discrimination standards makes it difficult to compare findingsby different practitioners, and at different medical facilities.

Also, because adjustment of color tone for normal tissue isconventionally performed and dependent upon the individual judgment ofthe medical practitioner, the absence of fixed calibration standardsrenders objective diagnosis by color tone difficult if not impossible.Resultantly, comparison of the white light image against the excitationlight image may be the most accurate means to discriminate diseased fromhealthy tissue. To accomplish this discrimination, switchingback-and-forth between white light and excitation light images isadvantageous. The switching becomes more critical in a therapeuticenvironment. If diseased tissue is discovered, the medical practitionermay need to excise the tissue while switching between the two images toensure all diseased tissue has been removed.

Further, due to conventional fluorescence diagnosis endoscope systemconstruction described above, only the light produced by thefluorescence of tissue is detected by the imager element of theendoscope. Thus, suspect tissue cannot be observed when illuminated withwhite light by the same endoscope. In some instances, to examine suspecttissue using white light, the endoscope designed for fluorescencediagnosis is removed and another endoscope for normal observation isinserted. This is time consuming, disruptive, and potentially hazardousto a patient during an examination and/or surgical procedure.

Various display schemes relating to differentiating normal tissue fromdiseased tissue are known. Generally, these display schemes fall into 4categories:

1. Diseased tissue view and normal tissue view displayedcombined/superimposed within a single video frame.

2. Diseased tissue view and normal tissue view displayedcombined/superimposed with alternating video frames.

3. Diseased tissue view and normal tissue view displayed separatelywithin a single video frames.

4. Diseased tissue view and normal tissue view displayed separatelywithin alternating video frames.

Depending upon how the excitation-light is generated and/or detected,this switching requires that a light source switch between a“white-light” mode and “excitation light” mode, and can be initiatedfrom the CCU (from a camera head button, for example).

Regardless of how the excitation light image is produced, eithersuperimposing the excitation light image over the white light image, ora side-by-side composite image, is typical. For example:

U.S. Pat. No. 4,556,057 to Hiruma et al. relates to a cancer diagnosisdevice which selectively illuminates a cancer focus with white light andlaser light synchronously with an imaging device, images of which arecoupled to a spectroscope for detecting spectral response.

U.S. Pat. No. 4,699,125 to Komatsu relates to storing superposed framesfrom an endoscopic video in response to a freeze instruction,photographing a frozen image displayed on a display means, andsequentially comparing image signals for a predetermined color componentin order to obtain a clear frozen image through motion detection.

U.S. Pat. No. 4,768,513 to Suzuki relates to analyzing fluorescencewavelength patterns for diagnostic purposes.

U.S. Pat. No. 4,791,480 to Muranaka relates to an endoscope having anadjustable light source which can be used to produce video and stillimages. When a still image is taken, the illuminating light can bepulsed during frame transfer from the solid state camera element inorder to avoid producing a blurred image.

U.S. Pat. No. 4,821,117 to Sekiguchi relates to alternately irradiatingan object with visible and excitation radiation and controlling theirradiating, storage, and displaying means to simultaneously display avisible radiation image and a fluorescent image.

U.S. Pat. No. 4,885,634 to Yabe relates to simultaneously displaying acolor image and a specific wavelength image on separate monitors or onthe same monitor screen.

U.S. Pat. No. 4,930,516 to Alfano et al. relates to exciting a tissuewith monochromatic lights and measuring the intensity of visible nativeluminescence emitted from the tissue of at least two wavelengths, anddisplaying a signal corresponding to the ration between the intensitiesof at least two wavelengths.

U.S. Pat. No. 5,034,888 to Uehara et al. relates to an electronicendoscope apparatus having different image processing characteristicsfor a moving image and a still image.

U.S. Pat. No. 5,507,287 to Palcic et al. relates to sending first andsecond spectral band autofluorescence images to the red and greenchannels of an RGB video monitor to create a combined display image.

U.S. Pat. No. 5,590,660 to MacAulay et al. relates to sendingautofluorescence and remittance light images to the red and greenchannels of an RGB video monitor to create a pseudo-color image.

U.S. Pat. No. 5,646,680 to Yajima relates to displaying either anendoscope video signal either through a peripheral device or directly sothat the peripheral device can be bypassed in case of a malfunction.

U.S. Pat. No. 5,647,368 to Zeng et al. relates to collecting colorfiltered excitation light and autofluorescence light and sending theimages to the red and green channels of an RGB video monitor to create afalse color contrast image.

U.S. Pat. No. 5,749,830 to Kaneko et al. relates to switching displaybetween simultaneous display and time-divided display of normalobservation video and fluorescent observation video.

U.S. Pat. No. 5,827,190 to Palcic et al. relates to storing andcombining sequential autofluorescence and reflectance images forsimultaneous display as a pseudo-color image.

U.S. Pat. No. 5,986,271 to Lazarev et al. relates to displaying asuperimposed or first and second region view of both a full color andresulting autofluorescence image.

U.S. Pat. No. 6,028,622 to Suzuki relates to displaying superimposedfluorescent images under different excitation lights.

U.S. Pat. No. 6,099,466 to Sano et al. relates to displaying a colorimage and/or a fluorescence image produced by processing fluorescencefiltered image signals.

U.S. Pat. No. 6,192,267 to Scherninski et al. relates to an angiographydevice for displaying contrast enhanced fluorescence images.

U.S. Pat. No. 6,293,911 to Imaizumi et al. relates to simultaneouslydisplaying an image under autofluorescence and white light insuperimposed or side-by-side format, and where a second image signal canbe subtracted from a first image signal.

U.S. Pat. No. 6,364,829 to Fulghum relates to display of sequentially orsimultaneously detected fluorescence and reference images.

U.S. Pat. No. 6,422,994 to Kaneko et al. relates to superimposing atissue fluorescence image color interpretation guide and an enhancedfluorescence image video.

U.S. Pat. No. 6,603,552 to Cline et al. relates to superimposingreflected light and fluorescence images.

U.S. Pat. No. 6,899,675 to Cline et al. relates to displayingsuperimposed video images from pixels of a low light color image sensorhaving one or more color filters.

U.S. Pat. No. 7,420,151 to Fengler et al. relates to simultaneouslydisplaying a white light and short-wavelength light image.

U.S. Pat. No. 7,965,878 to Higuchi et al. relates to an endoscopicsystem that stores matrix data for forming a spectral image and forms aspectral image in a selected wavelength band according to a matrixoperation on an original still image. The original still and one or morespectral images can then be displayed.

However the use of video having superimposed, interleaved, orside-by-side diagnostic and normal views as described above can beconfusing and lack clarity in many circumstances.

It is therefore desired to provide a device which addresses thesedeficiencies.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a stillimage of tissue under a particular type of illumination concurrentlywith a video image of the tissue under a different type of illumination.

This and other objects are achieved by providing an imaging system whichincludes an endoscope; a first source for providing illumination with afirst light; a second source for providing illumination with a secondlight; an imager for capturing video from the endoscope; a first displayarea for displaying a live video image; and a second display area fordisplaying a still image taken from the live video image prior to achange between illumination with the first light and illumination withthe second light.

In some embodiments, the first and second sources comprise a singledevice which can switch between the first and second lights.

In some embodiments, the first and second sources comprise differentdevices.

In some embodiments, the second display area is at least partiallywithin the first display area.

In some embodiments, the first display area and the second display areaare located on the same display device.

In some embodiments, the first light comprises visible light.

In some embodiments, the second light comprises an excitation light. Theexcitation light may include at least one wavelength which can activatea fluorescent or photodiagnostic substance.

In some embodiments, the second light comprises non-visible light.

Other objects of the present invention are achieved by providing animaging system which includes an endoscope; a first source forirradiating an object with a first light; a second source forirradiating an object with a second light; an imager for capturing avideo image from the endoscope; a first display for displaying the videoimage during irradiation with the first light; and, a second display fordisplaying a still image taken during irradiation with the second light.

Further objects of the present invention are achieved by providing animaging system which includes a control unit for receiving imageinformation from an endoscope that relates to an object, which cantransmit for display on a first display area a video image of theobject, and which can transmit for display on a second display areaconcurrently with the video image a still image of the object takenprior to a change in a wavelength of illumination of the object.

Still, further objects of the present invention are achieved byproviding a system for photodynamic diagnosis which includes a firstsource for providing illumination at a photodynamic wavelength; a secondsource for providing illumination at a non-photodynamic wavelength; animager for capturing video of tissue illuminated by the first source orthe second source; a first display area for displaying the video imageduring illumination at the first wavelength; and, a second display areafor displaying a still image taken from the video image duringillumination at the second wavelength.

In some embodiments, the first and second sources comprise a singledevice which can switch between the first and second wavelength.

In some embodiments, the first and second sources are provided bydifferent devices.

In some embodiments, the first display area and the second display areaoverlap.

In some embodiments, the first display area and the second display areaare located on the same display device.

In some embodiments, the first wavelength comprises visible light.

In some embodiments, the second wavelength comprises excitation light.The excitation light may include at least one wavelength which canactivate a fluorescent substance.

In some embodiments, the second wavelength comprises non-visible light.

Still further objects of the present invention are achieved by providinga method for creating a reference image during diagnostic imaging whichincludes selectively irradiating an object with a first light and asecond light; displaying a video image of the object; capturing a stillimage of the object immediately prior to switching between irradiatingthe object with the first and second light; and, displaying the stillimage concurrently with the video image.

In some embodiments, the first light is visible light.

In some embodiments, the second light is diagnostic light.

In some embodiments, the still image is displayed picture-in-picturewith the video image.

In various embodiments, the diagnostic light produces auto-fluorescencein a tissue and/or causes a drug to fluoresce.

In some embodiments, the both the first light and second light arediagnostic lights. Other objects of the invention and its particularfeatures and advantages will become more apparent from consideration ofthe following drawings and accompanying detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example system according to aspectsof the invention.

FIG. 2 is a block diagram showing another example system according toaspects of the invention that is a modification of the system shown inFIG. 1.

FIG. 3 is a block diagram showing another example system according toaspects of the invention that is a modification of the system shown inFIG. 1.

FIG. 4 is a flow chart illustrating operation of the example systemshown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The instant invention provides a recent “opposite mode” reference stillimage from the mode currently provided by live video, and displays the“opposite mode” reference still image on the monitor either as an insert(picture-in-picture, PIP), side-by-side, or the like concurrently withthe live video image.

For example, when a practitioner switches the light source from“excitation-light” to “white light”, the “excitation-light” video may befrozen/captured and displayed as a reference still image as a PIP, andthe “white-light” live video displayed as the primary video image.

Conversely, when the practitioner switches the light source from“white-light” to “excitation light”, the “white-light” video may befrozen/captured and displayed as a reference still image as a PIP, andthe “excitation-light” live video displayed as the primary video image.

It should be understood that while white light and excitation light areused as general terms for the sake of example herein, the invention isnot limited to these particular forms of light. For example, the systemmay switch between two distinct kinds of diagnostic light, between twodistinct kinds of non-diagnostic light, or among a greater number ofdiagnostic and non-diagnostic light. Also, the term light is used fromtime to time herein with respect to diagnostic illumination, however itis understood that in some embodiments light may include either visibleor non-visible wavelengths of electromagnetic radiation and/or photonicenergy.

FIG. 1 shows an example system 100 according to aspects of theinvention.

Example system 100 is an endoscopic system configured for diagnosingdiseased tissue 110. System 100 includes an endoscope with endoscopiccamera 120, light source 130, control module 140, and display 150.

Endoscopic camera 120 is shown as detachable from the endoscope, theendoscope being configured to emit light supplied by light source 130from the endoscope distal end 125 for illuminating diseased tissue 110.The light may be transmitted to the endoscope distal end 125 via one ormore optical fibers, or by other known methods.

Although endoscopic camera 120 is described as detachable from theendoscope in this example, other imaging devices can be used withoutdeparting from the invention, such as video endoscopes, flexibleendoscopes, variable direction-of-view endoscopes, solid state variabledirection-of-view endoscopes, and the like.

Light source 130 provides light to the endoscope distal end 125 forilluminating tissue 110. Light source 130 is capable of producing two ormore types of light. For example, light source 130 may supply whitelight, ultraviolet light, or other types of light, either concurrentlyor alternately, to the endoscope distal end 125 for illuminating tissue110.

Although light source 130 is shown as a discrete module in system 100,in alternative embodiments, light source 130 may be integrated into theendoscope or control module 140, for example. Light source 130 may alsobe implemented as two or more separate modules, each supplying light ofdifferent wavelengths, for example. Various permutations on thesearrangements that do not depart from the invention will be evident tothose having skill in the art. Light source 130 may be comprised of oneor more lamps, light-emitting diodes (“LEDs”) or other solid state lightsources, lasers, or other suitable light sources. The light produced bylight source 130 typically will be switchable between a white light anda diagnostic light having a wavelength(s) or spectrum optimized forproducing fluorescence or other contrast effects in tissue underobservation.

Under illumination by light from light source 130, tissue 110 reflectsand/or emits light in response depending upon the wavelengths of thelight. Endoscopic camera 120 receives the reflected and/or emitted lightfrom tissue 110. The emitted light may include light emitted bybiological structures through auto-fluorescence, light produced by thestimulated fluorescence of drugs administered to tissue 110, other knowntypes of light emissions, or several or all of these simultaneously.

Endoscopic camera 120 receives the light reflected and/or emitted fromtissue 110 and generates one or more image signals based on the lightreceived from tissue 110. The image signals are transmitted byendoscopic camera 120 to the control module 140.

Control module 140 may be a camera head module, camera control unit, orother imaging device, image receiving device, or other device thatreceives image data from endoscopic camera 120 and processes it fordisplay.

Control module 140 may also be in communication with light source 130 inorder to control its operation or to receive signals from light source130 as to its status or mode of operation. For example, light source 130may in some embodiments provide information to control module 140 as towhether it is supplying white or diagnostic light to endoscopic camera120, for example, or may indicate that the mode has changed or toggled,or may indicate its mode from among a number of illumination modesand/or types. In some embodiments, light source 130 may receive acommand from control module 140 to change its mode of operation fromwhite to diagnostic light, or from diagnostic to white light, forexample. In still another embodiment, both the light source 130 andcontrol module 140 may receive a light mode change signal from a commonsource, such as from a button on an endoscope or other instrument, forexample. Communication between control module 140 may take place via anyknown means, such as through a common signal connection with endoscopiccamera 120 or a separate signal connection, for example, to provideinformation about the light emitted by light source 130 to controlmodule 140.

Control module 140 transmits a video image 160 to display 150 that isproduced by processing image data received from endoscopic camera 120.For example, image 160 may be a video image of tissue 110 as illuminatedby a white light supplied by light source 130.

Control module 140 is also configured such that it can transmit a stillimage 170 to display 150 for display concurrently with video image 160.

When the mode of operation of light source 130 is switched, such that itsupplies diagnostic light to endoscopic camera 120 and stops supplyingwhite light, for example, control module 140 transmits a still image 170to display 150 which shows the last frame of the video image 160 takenunder the previous mode of operation (in this case, under white light).Control module 140 continues to transmit this still image 170 fordisplay on display 150 while concurrently transmitting video image 160for display on display 150. Thus in this scenario, image 170 shows thelast frame of video of tissue 110 that was taken while light source 130was supplying white light, while image 160 displays a live video imageof tissue 110 while it is being illuminated with diagnostic light bylight source 130.

Because non-fluorescing structures may not be as distinct underdiagnostic light, providing a still reference image of tissue 110illuminated under ordinary white light while showing live video oftissue 110 under diagnostic light has the advantage of assisting asurgeon to navigate such structures.

It should be noted that although image 170 has been described as showingthe last frame of video 160 taken in the previous mode of operation oflight source 130, it is understood that a different frame of video couldbe substituted in some embodiments without departing from the invention.For example, in some embodiments, image 170 may show a recent frame ofsuch video that is not precisely the last frame, without departing fromthe invention. This may be done, for example, to compensate forprocessing delays within control module 140 if necessary. Furthermore,while still image 170 is shown inset or overlapping video image 160 in apicture-in-picture (“PIP”) type display, in various embodiments theseimages can be reversed such that the video image is inset, or such thatimages 160, 170 may be shown side-by-side or otherwise arrangedseparately on display 150. Images 160, 170 may also be displayed onseparate monitors in some embodiments.

If the mode of operation of light source 130 is subsequently switched,such that it supplies white light to endoscope 120 and stops supplyingdiagnostic light for example, control module 140 transmits an updatedstill image 170 to display 150 which shows the last frame of the videoimage 160 taken under the previous mode of operation (in this case,under diagnostic light). Control module 140 continues to transmit thisupdated still image 170 for display on display 150 while concurrentlytransmitting video image 160 for display on display 150. Thus in thisscenario, image 170 will show the last frame of video of tissue 110 thatwas taken while light source 130 was supplying diagnostic light, whileimage 160 displays a live video image of tissue 110 while it is beingilluminated with white light by light source 130.

Displaying the last live video image as a reference still imageconcurrently with current live video image in this way can also have theadvantage of facilitating discrimination between healthy and diseasedtissue, and further facilitate therapeutic intervention.

Furthermore, using an updated still reference image for comparison witha video image can also have the advantage of reducing task overload byretaining a fixed familiar reference, while still being able to updatethe reference image on demand when and as required. Updating a stillreference image for comparison with a live video image in this way canprovide for improved situational awareness in critical medicalprocedures where the angle or orientation of view may be changed one ormore times.

It should be noted that in some embodiments where light source 130 hasmore than two modes of operation, control module 140 may be configuredto cycle images 160 and 170 with each mode change, such that video image160 shows live video taken under the current illumination mode and stillimage 170 shows the last frame of the video taken under the most recentmode. Because different biological structures and marking orfluorescence substances may respond differently to stimulation bydifferent wavelengths of diagnostic (or white) light, this can have theadvantage of allowing a surgeon to select from among a number ofdiagnostic wavelengths to provide the most useful reference and videoimages, for example.

FIG. 2 shows an example system 200 which illustrates variations onsystem 100 according to aspects of the invention.

System 200 is substantially identical to system 100 except that lightsource 130 is replaced with two light sources 130′, 130″, and images160, 170 are shown in a side-by-side arrangement on display 150.

The arrangement of images 160, 170 on display 150 may be madearbitrarily in some embodiments.

Using separate light sources 130′ 130″ may permit design or retrofit oflighting mode arrangements where it is desired to add a light sourcehaving different capabilities and/or structure. For example, lightsource 130′ may be a white light producing lamp, and light source 130″may be a laser which produces excitation light in a specific wavelengthor wavelength, for example.

FIG. 3 shows an example system 300 which illustrates other variations onsystem 100 according to aspects of the invention.

System 300 is substantially identical to system 100 except that anadditional display 350 has been added. In this embodiment, video image160 is shown on display 150 and still image 170 is shown on display 350.

Using separate monitors in this way can have the advantage of providinglarger images and permitting for more efficient workspace management insome embodiments.

FIG. 4 is a flow chart which illustrates the operation of systems 100,200, and 300 according to aspects of the invention.

400: During standard operation, live video is displayed continuouslyduring observation of a procedure, such as an endoscopic surgicalprocedure for example.

410: If a new mode of operation of the light source or sources isselected, a still image of the most recent frame of video taken underthe previous mode of operation is displayed.

420: thereafter, the illumination mode of the light source or sources isswitched to the new illumination mode, and display of live video (400)continues under the new illumination mode.

Although the invention has been described with reference to a particulararrangement of parts, features and the like, these are not intended toexhaust all possible arrangements or features, and indeed manymodifications and variations will be ascertainable to those of skill inthe art.

What is claimed is:
 1. An imaging system comprising: an endoscope; afirst source providing illumination with a first light; a second sourceproviding illumination with a second light; an imager capturing videofrom the endoscope; a first display area displaying a live video image;a second display area displaying a still image taken from a frame of thelive video image prior to a first change between illumination with thefirst light and illumination with the second light; and a control modulereceiving a user-generated light mode change via a signal from a usercontrol interface for toggling at least between illumination with thefirst light and illumination with the second light; wherein, in responseto each subsequent change between illumination with the first light andillumination with the second light initiated by the user controlinterface signal, both the first display area is updated to display adifferent live video image that is being captured after the respectivesubsequent change, and the second display area is updated concurrentlyto display a different still image that is taken from a frame of thelive video image prior to the respective subsequent change.
 2. Theimaging system of claim 1, wherein the first and second sources comprisea single device configured to switch between the first and secondlights.
 3. The imaging system of claim 1, wherein the first and secondsources comprise different devices.
 4. The imaging system of claim 1,wherein the second display area is at least partially within the firstdisplay area.
 5. The imaging system of claim 1, wherein the firstdisplay area and the second display area are located on the same displaydevice.
 6. The imaging system of claim 1, wherein the first lightcomprises visible light.
 7. The imaging system of claim 1, wherein thesecond light comprises an excitation light.
 8. The imaging system ofclaim 7, wherein the excitation light comprises at least one wavelengthwhich can activate a fluorescent or photodiagnostic substance.
 9. Theimaging system of claim 1, wherein the second light comprisesnon-visible light.
 10. An imaging system comprising: an endoscope; afirst source configured to irradiate an object with a first light; asecond source configured to irradiate an object with a second light; animager capturing a video image of said object from the endoscope; afirst display displaying the video image during irradiation with thefirst light; a second display displaying a still image taken from aframe of the video image during irradiation with the second light; and acontrol module receiving a user-generated light mode change via a signalfrom a user control interface for toggling at least between irradiationwith the first light and irradiation with the second light; wherein, inresponse to each change between irradiation with the first light andirradiation with the second light initiated by the user controlinterface signal, both the first display displays a video image that isbeing captured during a current irradiation with one of the first lightor second light, and the second display displays concurrently a stillimage taken from a frame of the video image during a previousirradiation with the other of the first light or second light.
 11. Animaging system comprising: a control module receiving image informationfrom an endoscope, said image information relating to an object withinview of said endoscope, wherein said control module is configured totransmit for display on a first display area a video image of theobject, wherein, concurrently with transmitting the video image, saidcontrol module is configured to transmit for display a still image thatis taken from a frame of the video image prior to a change in wavelengthof illumination of the object, wherein said control module is configuredto receive a user-generated light mode change via a signal from a usercontrol interface for toggling at least between illumination with afirst wavelength and illumination with a second wavelength, wherein, inresponse to each change in wavelength of illumination initiated by theuser control interface signal, the control module is configured toconcurrently transmit to the first display area an updated video imageof the object being illuminated under a current wavelength, and transmitto the second display area an updated still image taken from a frame ofthe video image prior to the respective change in wavelength ofillumination.
 12. The imaging system of claim 1, wherein the usercontrol interface comprises a button.